Tripp and Kooi were among the first wave of Iowans to head to the polls in the crucial swing state where early, in-person voting began yesterday. And they won't be the last. In increasing numbers, Americans will be heading to the ballot box early or voting absentee this year, and it has forced the campaigns and political parties to change the way they do business.

Early voting has drawn both proponents, who say it gives voters more opportunities to do their civic duty, and critics, who contend that Americans are casting their ballots with incomplete information. After all, we haven't even seen the candidates face off in their first debate yet.

But it does give both sides a chance to get their most committed voters to polls ahead of schedule so that they can focus on the undecideds closer to Nov. 6.

Four years ago, more than 30 percent of the vote was already in nationwide by Election Day, and the parties expect an even higher percentage this year. In battlegrounds like Ohio, upwards of 45 percent of all votes may be cast by Nov. 6, and in Nevada a whopping 75 percent of the vote could be in by the time Election Day rolls around.

However, as ABC News Political Director Amy Walter notes, the big question is: Who exactly is voting?

Republicans argue that they've got a very smart and sophisticated operation designed to target and turn out so-called "low propensity" voters: voters who lean Republican but don't always show up to vote.
But, Democrats may be benefiting from an increase in energy and enthusiasm from their base that could bring more of their folks to the polls. They can bank these votes now.